Add ocp-index-top

[reynir]

Ocp-index-top implements a toplevel directive #doc that can be used to lookup documentation using ocp-index's LibIndex module.

It is written by myself. It's a bit of a hack, and there's an issue with utop since utop 2.0.1 (see reynir/ocp-index-top#9). Because of the issues it's perhaps not 'awesome' enough, but I find it quite useful myself when exploring things in the toplevel.

[gasche]

I like the idea, but maybe we/you could restructure the list to have one ocp-index entry, which also points out to satellite projects, namely ocp-browser and ocp-index-top? (In the free text or as a sub-list.) This is already what we did for Menhir and Oasis for example.

[reynir]

I'm fine with that!

[Khady]

I think it worth mentioning ocp-grep here too. I'm sorry if it is already in, I don't have any internet to check the current content.

[rizo]

@reynir ocp-index-top is very handy, thanks for submitting the PR!

I rearranged the structure as suggested by @gasche and mentioned ocp-grep (there's no separate link for it unfortunately).

[reynir]

Hi @rizo, thank you for taking initiative!